Windows Environment Variables
Environment variables are mainly used within batch files, they can be created, modified and deleted for a session using the
SET command. To make permanent changes, use
Variables can be displayed using either
SET or
ECHO.
Variables have a percent sign on both sides:
%ThisIsAVariable%
The variable name can include spaces, punctuation and mixed case:
%_Another Ex.ample%
(This is unlike
Parameter variables which only have one % sign and are always one character long:
%A )
Standard (built-in) Environment Variables
| Variable | Volatile (Read-Only) | Default value in Windows 7/10/2008 (assuming the system drive is C: ) |
|---|---|---|
| ALLUSERSPROFILE | C:ProgramData | |
| APPDATA | C:Users {username}AppDataRoaming | |
CD | Y | The current directory (string). |
ClientName | Y | Terminal servers only – the ComputerName of a remote host. |
CMDEXTVERSION | Y | The current Command Processor Extensions version number. (NT = “1″, Win2000+ = “2″.) |
CMDCMDLINE | Y | The original command line that invoked the |
| CommonProgramFiles | C:Program FilesCommon Files | |
| COMMONPROGRAMFILES(x86) | C:Program Files (x86)Common Files | |
| COMPUTERNAME | {computername} | |
| COMSPEC | C:WindowsSystem32cmd.exe or if running a 32 bit WOW – C:WindowsSysWOW64cmd.exe | |
DATE | Y | The current date using same region specific format as DATE. |
ERRORLEVEL | Y | The current ERRORLEVEL value, automatically set when a program exits. |
| FPS_BROWSER_APP_PROFILE_STRING FPS_BROWSER_USER_PROFILE_STRING | Internet Explorer Default These are undocumented variables for the Edge browser in Windows 10. | |
| HighestNumaNodeNumber | Y (hidden) | The highest NUMA node number on this computer. |
| HOMEDRIVE | Y | C: |
| HOMEPATH | Y | Users {username} |
| LOCALAPPDATA | C:Users {username}AppDataLocal | |
| LOGONSERVER | \{domain_logon_server} | |
NUMBER_OF_PROCESSORS | Y | The Number of processors running on the machine. |
OS | Y | Operating system on the user’s workstation. |
| User and System | C:WindowsSystem32;C:Windows;C:WindowsSystem32Wbem; {plus program paths} | |
| PATHEXT | .COM; .EXE; .BAT; .CMD; .VBS; .VBE; .JS ; .WSF; .WSH; .MSC The syntax is like the PATH variable – semicolon separators. | |
PROCESSOR_ARCHITECTURE | Y | AMD64/IA64/x86 This doesn’t tell you the architecture of the processor but only of the current process, so it returns “x86″ for a 32 bit WOW process running on 64 bit Windows. See |
| PROCESSOR_ARCHITEW6432 | = %ProgramFiles% (only available on 64 bit systems) | |
PROCESSOR_IDENTIFIER | Y | Processor ID of the user’s workstation. |
PROCESSOR_LEVEL | Y | Processor level of the user’s workstation. |
PROCESSOR_REVISION | Y | Processor version of the user’s workstation. |
ProgramW6432 | = %PROCESSOR_ARCHITECTURE% (only available on 64 bit systems) | |
| ProgramData | C:ProgramData | |
| ProgramFiles | C:Program Files | |
ProgramFiles(x86) 1 | C:Program Files (x86) | |
| PROMPT | Code for current command prompt format,usually $P$G C:> | |
| PSModulePath | %SystemRoot%system32WindowsPowerShellv1.0Modules | |
| Public | C:UsersPublic | |
| Y | A random integer number, anything from 0 to 32,767 (inclusive). | |
%SessionName% | Terminal servers only – for a terminal server session, SessionName is a combination of the connection name, followed by #S essionNumber. For a console session, SessionName returns “Console". | |
| SYSTEMDRIVE | C: | |
| SYSTEMROOT | By default, Windows is installed to C:Windows but there’s no guarantee of that, Windows can be installed to a different folder, or a different drive letter. systemroot is a read-only system variable that will resolve to the correct location. NT 4.0, Windows 2000 and Windows NT 3.1 default to C:WINNT | |
TEMP and
| User Variable | C:Users {Username}AppDataLocalTemp Under XP this was {username} Local SettingsTemp |
TIME | Y | The current time using same format as TIME. |
| Y User Variable | Set if a user is a logged on to a domain and returns the fully qualified DNS domain that the currently logged on user’s account belongs to. | |
| USERDOMAIN | {userdomain} | |
| USERDOMAIN_roamingprofile | The user domain for RDS or standard roaming profile paths. Windows 8/10/2012 (or Windows 7/2008 with | |
| USERNAME | {username} | |
| USERPROFILE | %SystemDrive%Users {username} This is equivalent to the $HOME environment variable in Unix/Linux | |
| WINDIR | %WinDir% pre-dates Windows NT and seems to be superseded by %SystemRoot% Set by default as windir=%SystemRoot% %windir% is a regular variable and can be changed, which makes it less robust than %systemroot% |
1 Only on
64 bit systems, is used to store 32 bit programs.
Unless stated otherwise, all the variables above are System variables
Environment variables are stored in the registry:
User Variables:
HKEY_CURRENT_USEREnvironment
System Variables:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment
By default, files stored under
Local Settings do not roam with a roaming profile.
Dynamic environment variables are read-only and are computed each time the variable is expanded. When all variables are listed with SET, these will not appear in the list. Do not attempt to directly SET a dynamic variable.
Undocumented Dynamic variables (read only)
%__APPDIR__% The directory path to the current application .exe, terminated with a trailing backslash. (Global) –
%__CD__% The current directory, terminated with a trailing backslash. (Global)
%=C:% The current directory of the C: drive.
%=D:% The current directory of the D: drive if drive D: has been accessed in the current CMD session.
%DPATH% Related to the (deprecated)
DPATH command.
%=ExitCode% The hex value of the last return code set by
%=ExitCodeAscii% The
ASCII value of the last return code set by EXIT /B if greater than 32.
%FIRMWARE_TYPE% The boot type of the system:
Legacy ,UEFI,Not implemented ,Unknown Windows 8/2012.
%KEYS% Related to the (deprecated) KEYS command.
Undocumented Dynamic variables (read/write)
%__COMPAT_LAYER% Set the ExecutionLevel to either
RunAsInvoker (asInvoker),
RunAsHighest
(highestAvailable) or
RunAsAdmin(requireAdministrator) for more see
elevation and
Q286705 /
Application Compatibility Toolkit for other Compatibility Layers (colours,themes etc).
Pass variables between batch scripts
There are several ways to pass values between batch files, or between a batch file and the command line, see the
CALL and
SETLOCAL pages for full details.
A child process by default inherits a copy of all environment variables from its parent, this makes environment variables unsuitable for storing
secret information such as API keys or user passwords, especially in rare occasions like crashes where a crash log will often include the full OS environment at the time of the crash. PowerShell/Get-Credential is a more secure approach.